1. Field of the Invention
The present invention relates to a video output apparatus and a method for controlling the same.
2. Description of the Related Art
In recent years, broadcasting stations that broadcast three-dimensional video (3D video) have been appearing. Further, recording media (for example, Blu-ray discs) are also sold that contain content such as movies including 3D video. Display of 3D video is realized by utilizing the binocular parallax of the right eye and the left eye. As a main approach to display 3D video, there is a time division approach using glasses dedicated to stereoscopic vision.
In the time division approach, video to be viewed by the left eye or the right eye is alternately switched and displayed in certain units of time (generally, in units of frames or in units of fields). Glasses dedicated to stereoscopic vision can switch between penetration and non-penetration of the left and right lenses, using a liquid crystal shutter, for example. In synchronization with the switching cycle of video to be displayed, switching between penetration and non-penetration is performed. This enables a user to view 3D video.
It has been known that such simulated 3D video may have a harmful effect on a human body. For example, if the protruding amount of 3D video is equal to or larger than a certain amount, a symptom in which the brain is confused (so-called “3D sickness”) easily occurs due to the focus adjustment function of the eyeballs and spatial shifts of video being viewed. For this reason, the Japan Electronics and Information Technology Industries Association (JEITA), and the International Organization for Standardization (ISO) have been creating a guideline for a protruding amount.
Further, there is a problem in that if video including a large protruding amount is suddenly displayed (i.e., in a state in which a viewer is not mentally prepared) while viewing 3D video, the viewer feels greater surprise than usual. In consideration of the above problem, it has been proposed that information on the degree to which a specific viewer is influenced due to a protruding amount of three-dimensional video (3D video), and a protruding amount of the actual three-dimensional video are compared, and if the protruding amount is above an allowable degree for such a specific viewer, the protruding amount is adjusted (Japanese Patent Laid-Open No. 2006-270924).
However, in Japanese Patent Laid-Open No. 2006-270924, if a viewer's biological information is inaccurate, the protruding amount is limited more than necessary, so that the viewer is prevented from viewing 3D video with three-dimensional depth (protruding amount) that he or she expects. Further, a large-scale apparatus is necessary to acquire accurate biological information of viewers, which is not preferable in terms of man-hours for development or spread.